The present invention relates to the field of jet pumps.
The present invention finds particular but non-exclusive application in the field of motor vehicle fuel tanks.
Still more precisely, the present invention finds application in transferring fuel between different compartments in multi-compartment fuel tanks, or in filling a reserve bowl from which a fuel pump or any fuel feeder device draws fuel.
Examples of fuel suction devices based on jet pumps are shown in documents DE-A-3 915 185, DE-A-3 612 194, or DE-A-2 602 234.
Although known suction devices based on jet pumps have given good service, they nevertheless do not always give satisfaction.
An object of the present invention is to propose a novel and improved jet pump.
The invention seeks to mitigate those drawbacks.
To this end, the invention provides a jet pump comprising a housing containing a nozzle into which an injected fluid is introduced, the housing also possessing a suction orifice, the pump comprising, upstream from the outlet of the nozzle, an auxiliary chamber associated with two sealing elements, each sealing element being adapted to open when the pressure of the injected fluid exceeds a predetermined level, the first sealing element opening at a first pressure level, the second sealing element opening at a second pressure level greater than or equal to the first.
The invention advantageously further comprises the following characteristics taken singly or in any technical feasible combination:
the first sealing element is situated upstream from the auxiliary chamber, the second sealing element being situated downstream from the auxiliary chamber;
the first sealing element is situated upstream from the auxiliary chamber, the second sealing element being also situated upstream from the auxiliary chamber;
the nozzle is slidably mounted in the pump housing, to move along a longitudinal axis of the pump housing against bias from a spring urging it against a sealing element;
the first sealing element opens by means of the nozzle moving, the second sealing element being opened by limiting the displacement of a second moving element;
both sealing elements are opened by displacement of the nozzle;
the body of the nozzle comprises three portions: a central first portion generally in the form of a hollow circularly cylindrical tube of constant section; a second portion integrally molded on the outside surface of the central portion from the upstream end thereof and forming a drum extending towards the downstream end of the pump housing over the outside of the central portion; and a third portion situated downstream from the central portion having an outside shape that is substantially frustoconical and that converges downstream, its inside shape forming a nozzle outlet formed by a through axial channel connected to the inside volume of the central portion and opening out into a downstream suction chamber;
the space defined between the drum and the central portion forms a chamber open towards the downstream end of the pump and receiving the bias spring;
the general outside shape of the body of the nozzle in longitudinal section is substantially W-shaped, the two upstream bends of the W-shape forming a flat bottom defining a surface of generally annular shape lying in a transverse plane, facing upstream, and located inside the housing of the pump;
the annular surface has a longitudinal peripheral rim on its outer periphery extending towards the upstream end of the pump, said rim co-operating with a transverse gasket fixed to the housing of the pump and situated facing the annular surface to define a first sealing element;
the pump has a finger extending inside the inside volume of the central portion of the nozzle body, a cap movable in translation co-operating with a second bias spring which presses said cap against a transverse shoulder facing towards the upstream end of the pump and formed inside said central portion of the nozzle body, thus forming a second sealing element, which second sealing element is opened when the moving element reaches the end of its stroke as it follows the displacement of the nozzle body inside the pump housing, said displacement of the nozzle being due to the pressure of the injected fluid acting on the annular surface exceeding a second pressure level;
the central portion and the downstream portion of the nozzle both have the same inside diameter, the inside opening as defined in this way being extended at the upstream end of the nozzle by a circular longitudinally-extending rim integrally molded on the annular surface, said circular rim co-operating with a deformable gasket fixed on an element of the pump so as to form a sealing element, said sealing element opening as the nozzle moves forwards, said forward movement taking place when the pressure of the injected fluid reaches a second level; and
the inside shape of the third portion comprises, in the flow direction of the injected fluid, a first segment of converging frustoconical shape followed by a through second segment of circularly cylindrical shape of constant section.